Caltech Pickup - Caltech pickup Ultimate. They play almost daily in the summer, and 2-3 times a week during the school year, with games organized day-of via the mailing list.
Pasadena Pickup - Pickup ultimate in Pasadena. Usually higher level than the Caltech games.
Los Angeles Pickup - Pickup map of Los Angeles.
Find Pickup Games! - Going on vacation? You can use this to find ultimate pickup games in any city you might visit! This is actually the same website as above.
UltiWorld - Ultimate news and articles.
Caltech Mailing Lists - Other Caltech mailing lists. In case you have other interests, too.